Pneumatic switch



K. H. TOPFER .ET AL PNEUMATIC, SWITCH Filed May 9, 1966 Feb. 17, 1970 FIG. 2

INVENTORS United States Patent 3,495,611 PNEUMATIC SWITCH Karl Heinz Tiipfer, Dresden, Walter Dieter Schrepel, Friedewald uber Radebeul, and Karl August Arnulf Schwarz and Herbert Gtitz Dietmar Lang, Dresden, Germany, assignors to Deutsche Akademie der Wissenschaften zu Berlin, Berlin-Adlershof, Germany Filed May 9, 1966, Ser. No. 548,703 Int. Cl. G05d 11/02; F1611 11/06 US. Cl. 137-12 3 Claims ABSTRACT OF THE DISCLOSURE The invention is concerned with a pneumatic switching device for converting mechanical motion into pneumatic signals in which a pneumatic relay has operatively connected thereto a control member which communicates with one of the fluid chambers of the relay. The control member has a passage forward therein which communicates the relay chamber with the atmosphere. An actuating element axially disposed with respect to the passage and adapted to seal or open such passage by moving on a very short distance thereby effecting a change in the state of the operating fluid in such chamber, whereupon a signal is produced by the relay at its output.

The invention relates to pneumatic precision switches in general, and more particularly it relates to a pneumatic precision switch capable of converting an extremely small mechanical displacement into a pneumatic signal of high accuracy.

Pneumatic switches are known which are mechanically actuated multi-way valves in which the flow of a compressed air stream is changed by a control slide, or by a valve member having a plurality of valve seats. The actuation of such multi-way valves requires long switching paths and relatively great operating force because of such long paths. This circumstance renders these multiway valves inadaptable as precision switches.

Furthermore, pneumatic spring switches are known, wherein a ball or a cylindrical body is mounted in a bore having close tolerances, and closes a small air passage by means of a spring. If the ball or the cylindrical body is lifted away from the small passage by means of a plunger, the spring switch is instantly separated from the passage. The disadvantage of such spring switch resides in that it is only capable of triggering a pneumatic signal. For turning the signal off, it requires an additional three-way valve, which renders the practical use of such switches rather complicated, if not impossible, in many applications.

It is, therefore, an object of the invention to provide an improved pneumatic precision switch.

:It is another object of the invention to provide an improved pneumatic precision switch which is capable of producing high precision pneumatic switching signals repeatedly in response to an extremely small mechanical control movement.

It is a further object of the invention, to provide an improved pneumatic precision switch which is capable of producing high precision pneumatic switching signals in response to a small mechanical control movement and, which requires only small operating power to produce a strong output signal, the latter being useful in many applications without amplification.

It is still another object of the invention to provide an improved pneumatic precision switch which combines advantageously, the features of a membrane controlled pneumatic relay with that of a mechanically actuating member, in which the actuating member in response to ice a small mechanical control force acting over an extremely short path, controls the output of the membrane relay.

In accordance with the invention, the pneumatic switching device for converting mechanical motions into pneumatic signals comprises pneumatic switch means operable with a fluid and having input and output means, and an actuating member operatively coupled to the pneumatic switch means for effecting a change in the state of the fluid in response to mechanical movements transmitted to the actuating member, whereby a signal is produced at the output of the pneumatic switch means.

In accordance with the invention, an actuating base or control member is connected directly or indirectly to a membrane controlled pneumatic relay in communicating relationship with an operating chamber of such relay. The base or control member has formed therein a pas sage connecting the operating chamber of the pneumatic relay with an external medium. An actuating element acts over an exceedingly short path to open or close this passage in response to mechanical pressure applied to the element, the actuating element being guided within or outside of the base member. Accordingly, opening or sealing of the aperture effects a change in the state of an operating fluid in the chamber of the pneumatic relay, whereupon a signal is produced by the relay at its output.

In an embodiment of the invention, the actuating element is guided within a guide member disposed externally of the base member, and the actuating element is aligned with a passage through the base member between the operating chamber of the pneumatic relay with the external medium, so that application of an external mechanical force to the actuating element moves it away from sealing engagement with the passage through the base member. Thus, the passage in the base member is free to communicate between the operating chamber of the relay and the external medium.

In accordance with another embodiment of the invention, the actuating element is guided within the base member, and a compression spring biases the actuating element against a seat formed adjacent the passage in the base member connecting the base member with the external medium. Upon actuation, the element is moved off of the seat against the force of the biasing spring, and the operating chamber of the pneumatic relay is placed in communication with the external medium.

In a still further embodiment of the invention, the actuating element is guided within the base member to seat upon or move away from a like valve seat. Instead of the compression spring mentioned in the above-named embodiment, a further passage is provided in the base member which supplies a portion of the operating fluid of the pneumatic relay to seat the actuating element upon the valve seat. Upon being acted upon by an external mechanical force, the actuating element moves against the air cushion of the portion of the relay operating fluid to open the communication between the operating chamber of the relay and the external medium.

The invention will become more readily apparent from the following description of preferred embodiments thereof shown in the accompanying drawings, in which:

FIG. 1 is a schematic showing the pneumatic relay, its base member and its actuating element in accordance with the invention;

FIG. 2 is a schematic showing of another embodiment of the invention; and

FIG. 3 is a still further embodiment of the invention.

With reference to the drawings, it is seen that a doublemembrane pneumatic relay 1 is combined with an actuating base member 2. The double-membrane relay being the same in all the illustrated embodiments, therefore, will be described in detail only in connection with FIG. 1.

The double-membrane relay 1 includes membranes 22 and 23 connected by a spacing member 30 to insure that movement of one membrane is correlated with movement of the other. The membranes define a plurality of operating chambers within the relay, such as chambers 31 and 32 positioned externally of the membranes. The portion of the relay positioned internally of the membranes contains a pair of annular elements 19 and 20 which define three chambers 35, 33 and 34 within the internal portion of the relay. Chambers 33 and 34 are defined by membranes 23 and 22 and by the annular elements 20 and 19, respectively. A central chamber 35 is formed between annular elements 19 and 20. An operating fluid, which is preferably air at a pre-determined pressure, is supplied to the operating chambers 32, 33, 34 and 31 through inputs 17, 15, 24 and 25 respectively, from a source 11 of pneumatic operating fluid, schematically shown. The centrally located chamber 35 supplies the output signals through an output 12 under conditions described hereinafter. With respect to details of operation and detail structural aspects of the double membrane relay, reference may be had to co-pending application Ser. No. 479,533, filed Aug. 13, 1965, now abandoned, assigned to the assignee of the present application, and entitled Membrane Relay for Control and Regulating Devices.

With reference to FIGURE 1, it is seen that a base or control member 2 is suitably secured to the membranerelay housing. The base member 2 has formed therein a passage 4 extending therethrough which affords communication between control chamber 31 of the membrane-relay and an external medium, such as air. A guide member 3 is spaced from base member 2 and has an aperture therethrough which has disposed therein in sliding relationship therewith, an actuating element 5. The actuating element is axially aligned with the passage 4, in the base hinge 2, and is of greater diameter than this passage. At its end nearest the passage 4, the actuating element is given a conical shape Thus, when a mechanical force acts on actuating element 5 in the direction of the base members 2, such force causes the actuating element 5 to be displaced toward the base member 2 and to close the passage 4 therein. The operating fluid entering the chamber 31 through input 25 thereupon builds up pressure in that chamber, while the operating fluid in the chamber 34 is free to leave that chamber, to enter the central chamber 35 and to leave the central chamber 35 through its outlet 12, until the diaphragm 22 contacts the axially-extending flanges of the annular element 19 to close the chamber 34. No operating fluid from the chamber 34 leaves the switch through the outlet 12. This condition may be used to create a signal.

When a mechanical force acts to move the actuating element 5 in opposite direction, the diaphragm returns to its original position. Then the operating fluid from the chamber 34 leaves the switch through the outlet 12, thus restoring the original flow of the fluid through the outlet 12 and thereby creating a second signal, if desired.

According "to the same principles, the relay may be operated from a starting position in which the actuating element 5 initially closes the passage 4.

Other variations in the operation of the membrane relay are possible in dependence of various signals applied at the different inputs, which becomes more clear from the examples given in the above-mentioned co-pending application.

Since the double-membrane relay is the same in the embodiments of FIGS. 2 and 3, it will not be described in detail in connection with the control members of these further embodiments.

With reference to FIG. 2, it is seen that the base member includes a bore '14 of increased diameter which is in communication with passage 4 and with operating chamler 31. The bore 14 contains the head portion 13 of the actuating element 5a which is formed with a stern portion 6 extending through passage 4 into engagement with the source of the mechanical control force. The head portion 13 is biased by a compression spring 8 against a valve seat formed at the end shoulder of the bore 14 on which a gasket 7 is disposed for improved sealing engagement of the head portion to form a fluid tight seal therewith. Under operational conditions, as described above, when a mechanical force acts upon stern portion 6, it forces the actuating element 5a against the force of compression spring 8 away from the valve seat and gasket 7 so that a communication is established between the external medium and chamber 31 which leads to similar results, as abovedescribed. Upon discontinuance of the mechanical force, the compression spring returns the head portion 13 of the actuating element to its original position, i.e. in fluid tight relationship with gasket 7, so that a pressure may build up in operating chamber 31 again.

With reference to FIG. 3, it is seen that actuating element 5b includes a piston-like head portion 27 which slides in fluid-tight relationship in a bore 14. In this embodiment the compression spring is dispensed with, and instead, an air cushion =10 is used to bias the actuating element into engagement with valve seat 7 to seal off the communication between the operating chamber 31 and the external medium. The air cushion is formed through the application of fluid from source 11 through a passage 28 against the inner-end of head portion 27 of actuating element 5a for forcing the head portion into fluid-tight relationship with gasket 7. When a mechanical force acts upon the stern portion 9 of actuating element 5b, it displaces the actuating element away from the valve seat 7, whereupon a communication is established between operating chamber 31 and the external medium through passage 29 and passage 4 with which the stern portion 9 of the actuating element forms a clearance permitting fluid-flow out of the chamber 31. Operation of the device of FIG. 3 is similar to the operation of the device described in connection with FIGS. 1 and 2.

It is seen that the invention provides a high precision pneumatic switch which is capable of converting mechanical signals acting on an extremely short path, into reliable pressure signals by employing minimum moving elements within the device.

What is claimed is:

1. A pneumatic switch for converting mechanical motions into pneumatic signals, comprising a pneumatic relay having at least an output, an input, and a control chamber, said chambers being consecutively arranged around a central axis said output chamber communicating with said input chamber through an inner passage projecting into the input chamber concentrically with said central axis; pressure input means provided for said pressuer input and control chambers, respectively, and pressure output means for connecting said pressure output chamber with an outer medium, a membrane separating said pressure input chamber from said pressure control chamber and being adapted to control said inner passage in response to the pressure difference between the pressures in said pressure input and control chambers; said control chamber communicating with the outer medium through an outlet passage arranged concentrically and substantially in alignment with said central axis; and an actuating element disposed for axial movement in operative proximity to said outlet passage to control the same and thus the pressure difference between the pressures in said input and control chambers; a central portion of said outlet passage including a bore of increased diameter, said actuating element comprising plunger means including a head portion disposed in said bore with clearance therewith and a stem portion projecting through said outlet passage with a clearance therewith, said bore having a shoulder portion forming a sealing seat for said head portion.

5 6 2. A pneumatic switch as claimed in claim 1, further 2,608,342 8/1952 Aileman 137-119 X including spring means biasing said head portion into 3,110,469 11/1963 Becker 251-45 sealing relationship with said shoulder portion. 3,282,556 11/ 1966 Hancock 251-45 X 3. A pneumatic switch as claimed in claim 1, said bore 3,369,565 2/1968 Haggard 251-45 X including a section of reduced diameter and said head portion being adapted to be displaced in said section in F REI N PATENTS fluid tight relationship therewith, said control chamber 110 425 4 19 '4 Czechoslovakia comprising a further passage supplying said fluid against 7 said head portion for urging said head portion against WILLIAM F. ODEA, Primary Examiner sald shoulder portion 10 D. J. ZOBKIW, A ssistant Examiner References Cited 7 UNITED STATES PATENTS 137119, 625.66

1,575,771 3/1926 King 137-112 X 15 2,000,002 4/1935 Stockmeyer 251-45 X 'Us. 01. X.R. 

